Inserting and decoding replicated data symbols in wireless communications

ABSTRACT

Examples are generally described that include transmission methods including inserting at least a portion of data from a first data stream into a second data stream to be transmitted over a communications channel. On receipt of the two data streams, examples of receiving methods include receiving the replicated data, decoding the replicated data using an estimated channel matrix, and generating an updated estimate of the channel matrix based, at least in part, on the replicated data.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Multiple-input multiple-output (MIMO) communication systems employmultiple transmit antennas and multiple receive antennas to communicatedata symbols over a communications channel. MIMO communication systemsmay allow a plurality of mobile stations to be serviced utilizing a samefrequency band. In this manner, MIMO communication systems mayadvantageously increase an amount of data the communication systems isable to send to users.

MIMO systems may find use in a variety of applications including, butnot limited to, wireless networks, cellular systems including 3G and 4Gsystems, such as 3GPP LTE-Advanced, local and wide area networks, andwireless broadband systems (such as WiMAX).

Generally, a transmitter in a MIMO system may have a plurality ofantennas. Receiving devices may each have a single antenna for receiptof data over the communications channel, or may have multiple antennas.

The communications channel, however, may introduce a variety ofnon-idealities to a transmitted signal, such as may be caused bymultipath interference, reflections, motion of one or more mobilestations, or other properties of a communications channel. The signalsreceived by a receiver over the communications channel may be related tothe transmitted signals by a channel matrix H. The channel matrixgenerally refers to a matrix of data which may represent the operationof the communications channel on the transmitted data symbols, includingrepresentations of such effects as reflections.

Orthogonal frequency division multiplexing (OFDM) modulation techniquesmay be used to modulate data for transmission over a communicationschannel. OFDM generally involves modulating different portions of thedata to be transmitted using different sub-carrier frequencies.

Block coding techniques may be used in communication systems to encodedata and transmit multiple data streams over a communications channel,which may improve the reliability of data transfer. Block codingtechniques include space-time block coding, which may transmit multipledata streams across multiple antennas. Alamouti space time block codingis one particular type of space-time block coding known in the art.Space-time block coding techniques may require that the communicationschannel be constant during consecutive data transmission times, whichmay not always be advantageous. Another type of block coding techniqueis space-frequency block coding. Alamouti space-frequency block codingis one particular type of space-frequency block coding known in the art.Space-frequency block coding techniques may require that differentfrequencies experience similar communications channel properties, whichmay be more advantageous in some cases.

Block coding techniques may commonly be used in conjunction with OFDM.Decoding of block encoded OFDM transmissions may require knowledge ofproperties of the communications channel over which the transmission isreceived. Accordingly, systems utilizing block encoded OFDMtransmissions generally measure one or more properties of thecommunications channel, such as the channel matrix. One way to measureproperties of the communications channel is to insert pilot symbols intothe transmitted data streams. The pilot symbols may be known to thereceiver and the known pilot symbols may be compared with the receivedsignals to generate an estimate of one or more properties of thecommunications channel. The need to insert pilot symbols into thetransmitted data streams may adversely effect a data rate attainable inthe communications system.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several examples in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings, in which:

In the drawings:

FIG. 1 is a schematic illustration of an example system that isconfigured for communication over a communications channel in accordancewith at least some examples of the present disclosure;

FIG. 2 is a schematic illustration of components of the communicationsdevice 110 arranged in accordance with examples of the presentdisclosure;

FIG. 3 is a schematic illustration of signals transmitted over acommunications channel in accordance with examples of the presentdisclosure;

FIG. 4 is a schematic illustration of components of the communicationsdevice 115 arranged in accordance with examples of the presentdisclosure;

FIG. 5 is a schematic illustration of signals transmitted over thecommunications channel in accordance with some examples of the presentdisclosure;

FIG. 6 is an example method for transmitting signals over acommunications channel arranged in accordance with an example of thepresent disclosure;

FIG. 7 is an example method for receiving signals over a communicationschannel arranged in accordance with an example of the presentdisclosure; and

FIG. 8 is a block diagram illustrating an example computing device 800that is arranged for generating an updated channel estimate inaccordance with examples of the present disclosure.

SUMMARY

The present disclosure describes a method of transmitting data over acommunications channel. Some example methods may include modulatingdata, inserting data from one stream into another stream, and/ortransmitting the data streams over a communications channel. Themodulation may be performed in accordance with an orthogonal frequencydivision multiplexing technique, and may generate at least a first andsecond data stream for transmission using respective transmit antennas.The inserting may insert at least a portion of data from the first datastream into the second data stream.

The present disclosure describes methods of decoding a signaltransmitted over a communications channel. Example methods may include,receiving a pilot symbol over the communications channel, estimating achannel matrix of the communications channel based, at least in part, onthe pilot symbol, receiving replicated data from multiple data streamstransmitted over the communications channel, decoding the replicateddata using the estimated channel matrix, and/or generating an updatedestimate of the channel matrix based, at least in part, on thereplicated data.

The present disclosure describes communications devices. Examplecommunications devices may include a modulator, a replicator, anencoder, and/or a transmitter. The modulator may be configured tomodulate data in accordance with an orthogonal frequency divisionmultiplexing technique for transmission over a communications channelusing at least a first and a second transmit antenna. The modulator maybe further configured to generate at least a first data stream fortransmission with the first antenna and a second data stream fortransmission with the second antenna. The replicator may be coupled tothe modulator and configured to receive the first and second datastreams. The replicator may also be configured to insert at least onedata symbol from the first data stream into the second data stream. Theencoder may be coupled to the replicator and may be configured toreceive the first and second data streams including the inserted atleast one symbol. The encoder may be configured to encode the first andsecond data streams in accordance with a block coding technique. Thetransmitter may be coupled to the encoder and may be configured toreceive the encoded first and second data streams. The transmitter maybe configured to transmit the first data stream over the communicationschannel using the first antenna and further configured to transmit thesecond data stream including the inserted at least one symbol over thecommunications channel using the second antenna.

Example communications devices may include a receiver, a decoder, and/ora channel estimator. The receiver may be configured to receive signalsover a communications channel, wherein the signals are based at least inpart on first and second data streams transmitted over a communicationschannel, wherein the second data stream includes at least one datasymbol replicated from the first data stream. The decoder may be coupledto the receiver and the channel estimator. The decoder may be configuredto receive the received signals and decode the at least one data symbolreplicated from the first data stream. The channel estimator may becoupled to the decoder and the receiver, and may be configured toreceive the received signals and the decoded at least one data symbol.The channel estimator may be configured to estimate a channel matrix ofthe communications channel based, at least in part, on the decoded atleast one data symbol. The decoder may also be configured to decodesubsequent received signals based, at least in part, on the estimate ofthe channel matrix.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

DETAILED DESCRIPTION

The following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative examples described in the detaileddescription, drawings, and claims are not meant to be limiting. Otherexamples may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in theFigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which areimplicitly contemplated herein.

This disclosure is drawn, inter alia, to methods, systems, devices,and/or apparatus generally related to use of replicated data as a pilotsymbol in a communications system. Examples of transmission methodsinclude inserting at least a portion of data from a first data streaminto a second data stream to be transmitted over a communicationschannel. On receipt of the two data streams, examples of receivingmethods include receiving the replicated data, decoding the replicateddata using an estimated channel matrix, and generating an updatedestimate of the channel matrix based, at least in part, on thereplicated data.

FIG. 1 is a schematic illustration of an example system that isconfigured for communication over a communications channel in accordancewith at least some examples of the present disclosure. A system 100 maybe a multiuser multiple-input multiple-output system configured forcommunication over a communications channel 105. System 100 may includea communications devices 110, 115, 116, and/or 117. The communicationsdevices may be operated by users (not shown).

The communications device 110 may be implemented as a base station andmay be configured to communicate with multiple mobile stations 115, 116,and 117. The communications device 110 may include antennas 112 and 114,which may be utilized to communicate over the communications channel 105using multiple antennas for spatial diversity to communicate withmultiple users over each frequency.

The communications device 110 may include antennas 112 and 114, anencoder 158, a transmitter 160, a replicator 162, and/or a modulator164. Antennas 112 and 114 may be coupled to the transmitter 160. Theencoder 158 may be coupled to transmitter 160. The modulator 164 may becoupled to encoder 158. The replicator 162 may be coupled to modulator164 and encoder 158.

The modulator 164 may be configured to receive data for transmissionover the communications channel 105. The modulator 164 may be configuredto modulate the data in accordance with one or more modulationtechniques, such as orthogonal frequency division multiplexing (OFDM).Any suitable modulator may be used, and modulator 164 may be implementedin hardware, software, or combinations thereof. The modulator 164 mayaccordingly generate multiple data streams for communication over thecommunications channel, one for transmission using each of therespective antennas 112 and 114 in some examples. Pilot symbols may beinserted into the data streams by the modulator 164 or may be insertedbefore or after the modulator 164 in some examples.

The replicator 162 may be configured to receive one or more data streamsgenerated by the modulator. The replicator 162 may be configured toreplicate at least a portion of data from one data stream and insert thereplicated data into another data stream, as will be described furtherbelow. Any suitable hardware, software, or combinations thereof may beused to implement the replicator 162, including a mixer.

The encoder 158 may be configured to receive one or more data streamsgenerated by the modulator 164 and which may have been modified by thereplicator 162. The encoder 158 may be configured to encode the datastreams in accordance with a block encoding technique, such asspace-time or space-frequency block coding, including in some examplesAlamouti space-time or Alamouti space-frequency block coding.

The transmitter 160 may be configured to transmit the encoded data overthe communications channel 105 via the cooperative operation of thetransmitter 160 and one or more of antennas 112 and/or 114.

Although not shown in FIG. 1, the communications device 110 may alsoinclude components configured to receive, decode, and demodulate signalsreceived over the communications channel. That is, the communicationsdevice 110 may both send and receive signals over the communicationschannel in some examples.

The communications device 115 may include antenna 119, a receiver 172, adecoder 174, a channel estimator 178, and/or a demodulator 170. Antenna119 may be coupled to the receiver 172 and the channel estimator 178.The channel estimator 178 may also be coupled to the decoder 174. Thedemodulator 170 may be coupled to the decoder 174.

The receiver 172 is configured to cooperate with antenna 119 to receivesignals over the communications channel 105 and provide the receivedsignals to decoder 174. Although not shown in FIG. 1, in some examples,multiple antennas may be provided at the communications device 115. Inexamples using Alamouti encoding and decoding, however, a single receiveantenna may generally be used to receive signals over the communicationschannel 105. Any suitable receiver may be used and the receiver 172 maybe implemented in hardware, software, or combinations thereof. As willbe described further below, the received signals may include data

The decoder 174 may be configured to decode signals received from thereceiver 172 to provide data. Any of a variety of decoding techniquesmay be used in accordance with a technique used to encode the signalsreceived by the receiver 172. Examples of decoding techniques includeblock decoding techniques including space-time and space-frequency blockdecoding, and Alamouti space-time and space-frequency decoding in someexamples. Any suitable decoder may be used and the decoder 174 may beimplemented in hardware, software, or combinations thereof.

The demodulator 170 may be configured to demodulate decoded data fromthe decoder 174. The demodulator 170 may generally implement anydemodulation technique, including demodulation in accordance withorthogonal frequency division multiplexing (OFDM) techniques. Anysuitable demodulator may be used, and the demodulator 170 may beimplemented in hardware, software, or combinations thereof.

The channel estimator 178 may be configured to estimate all or a portionof a channel matrix H associated with the communications channel 105. Aswill be described further below, the channel estimator 178 may utilizepilot symbols to estimate the channel matrix. The channel estimator 178may also be configured to use decoded replicated data as a pilot symbolto estimate the channel matrix and/or update an estimate of the channelmatrix. By utilizing replicated data to generate or update an estimateof the channel matrix, the communications device 115 may in someexamples require fewer pilot symbols to be inserted into signalscommunicated over the communications channel 105. Reducing a number ofpilot symbols inserted into the transmitted signals may advantageouslyimprove the data rate of the communications system 100 in some examples.

Although not shown in FIG. 1, the communications device 115 may alsoinclude components such as a transmitter, encoder, and/or modulator, fortransmitting signals over the communications channel 105. That is, insome examples, the communications device 115 may both transmit andreceive signals over the communications channel.

Communications devices 116 and 117 may be similarly configured tocommunications device 115. The communications device 116 may includeantenna 121. The communications device 117 may include antenna 123.

The communications channel 105 may generally include any suitable mediumfor transmitting electromagnetic signals. The communications channel 105may be characterized by the channel matrix H describing the operation ofthe communications channel 105 on transmitted symbols. The channelmatrix H may provide a representation of effects such as reflections inthe communications channel. The channel matrix H may vary over time, andmay be calculated periodically in some examples. While a singlecommunications channel 105 is illustrated in FIG. 1, any number ofcommunications channels may be used.

Any number of communications devices may be included in thecommunications system 100, including the communications devices 115,116, and 117. Although not shown, the communications devices 116 and 117may include analogous components to those shown in mobile station 115.The communications devices 115, 116, and 117 may be implemented asmobile stations in some examples.

FIG. 2 is a schematic illustration of components of the communicationsdevice 110 arranged in accordance with examples of the presentdisclosure. The modulator 164 may include a mapping and pilot insertionblock 202, which may be coupled to a serial to parallel converter 204,which may be coupled to an inverse Fourier transform (IFFT) block 206,which may be coupled to a parallel to serial converter 208. Thereplicator 162 may be coupled to the parallel to serial converter 208.The encoder 158 may be coupled to the replicator 162.

During operation, data for transmission over a communications channelmay be provided to the mapping and pilot insertion block 202, which maybe configured to map the data to symbols and insert pilot symbols intothe data stream. In some examples, the pilot symbols may be inserted ata later point in the signal processing stream. The serial to parallelconverter 204, IFFT 206, and parallel to serial converter 208 may beconfigured to modulate the data stream in accordance with an OFDMtechnique to generate multiple data streams for transmission over thecommunications channel. The replicator 162 may replicate a portion ofthe modulated data such that some data symbols from one stream areinserted into another stream. The space-time encoder 158 may then encodethe data streams, including inserted symbols, for transmission over thecommunications channel. The configuration of FIG. 2 may provide forspace-time encoding of the data streams.

FIG. 3 is a schematic illustration of signals transmitted over acommunications channel in accordance with examples of the presentdisclosure. The signals 302, 303, 304, and 305 of FIG. 3 may betransmitted by the transmitter 160 of FIG. 1 in some examples, andreceived by the receiver 172. The example of FIG. 3 illustrates signalsencoded using a space-time block coding technique. In particular,signals 302 and 303 may be transmitted during a first time period whilesignals 304 and 305 are transmitted during a second time period. Signals302 and 304 may be transmitted from one location, such as by the antenna112 of FIG. 1. Signals 303 and 305 may be transmitted from anotherlocation, such as by the antenna 114 of FIG. 1. The relationshipsbetween the signals 302, 303, 304, and 305 may generally be specified bythe space-time coding technique used. Each of the illustrated signalsmay encode multiple data symbols, shown as boxes in FIG. 3. For example,the signal 302 may encode the symbols 310-317. Pilot symbols may also beencoded by the signals. In the example of FIG. 3, the symbols 310 and314 may represent pilot symbols. The pilot symbols 310 and 314 mayaccordingly also be present at similar frequencies in the signal 303.Further, replicated data symbols from the signal 302 may be included inthe signal 303. In this example of FIG. 3, the data symbols 312 and 316may have been replicated to symbol locations at correspondingfrequencies at the second spatial location, as shown. Additional datasymbols 318-321 may be included in the signals 303.

The example of FIG. 3 illustrates replicated data symbols inserted at amidpoint between two pilot symbols in a data stream. In other examples,replicated data symbols may be inserted at a location other than amidpoint between two pilot symbols, and the replicated data symbol maybe inserted at a location closer to one pilot symbol than another. Insome examples, some pilot symbols may have no replicated data symbolsinserted between them. In general, any number or arrangement ofreplicated data symbols may be inserted into a data stream. As will bedescribed further below, the replicated data symbols may be utilized ina manner similar to pilot symbols to estimate the communicationschannel. Since the replicated data symbols also encode data, the use ofreplicated data symbols as pilot symbols may increase the data rate ofthe over communications system in some examples.

FIG. 4 is a schematic illustration of components of the communicationsdevice 115 arranged in accordance with examples of the presentdisclosure. The demodulator 170 may include a serial to parallelconverter 402, a fast Fourier transform unit (FFT) 404, a parallel toserial converter 406, and a mapping block 408. The serial to parallelconverter 402 may be coupled to the FFT 404. The FFT 404 may be coupledto the channel estimator and a space-time decoder 174. The space-timedecoder 174 may be coupled to the parallel to serial converter 406. Theparallel to serial converter 406 may be coupled to the mapping block408.

In operation, signals received by the receiver 172, such as the signals302-305 of FIG. 3, may be provided to the serial to parallel converter402 and converted into parallel streams. The FFT 404 may perform aFourier transform of the streams, and provide the Fourier transformedsignals to the channel estimator 178 and the space-time decoder 174. Inaccordance with the methods described below, the channel estimator 178may estimate all or a portion of the channel matrix based on receivedpilot symbols and/or replicated data symbols. The space-time decoder 174may decode the data streams in accordance with the estimated channelmatrix. Moreover, the space-time decoder 174 may provide signalsindicative of the replicated data symbols to the channel estimator 178.The replicated data symbols may be used by the channel estimator 178 toestimate all or a part of the channel matrix, or to update an estimateof the channel matrix. Decoded signals may be provided from thespace-time decoder 174 to the parallel-to-serial converter 406 andconverted into a serial data stream of decoded symbols. The symbols maybe provided to the mapping block 408 and may be converted into a streamof output data. In this manner, data may be encoded, transmitted,received, and decoded in the communications system in some examples.

In some examples, the positioning of the encoder and decoder relative tothe FFT and IFFT blocks of the modulator may vary. In particular, theconfiguration shown in FIG. 4 may correspond to examples usingspace-time coding and decoding techniques. In some examples,space-frequency coding and decoding may be used. In examples wherespace-frequency coding is used, the encoder 158 may be coupled betweenthe serial to parallel converter 204 and the IFFT 206.

FIG. 5 is a schematic illustration of signals transmitted over thecommunications channel in accordance with some examples of the presentdisclosure. The example shown in FIG. 5 may pertain to examplesemploying space-frequency coding techniques. Input data symbols 505including symbols labeled S1-S11 may be provided to the modulator 164 ofFIG. 1. Following modulation, pilot insertion, data replication, andcoding in accordance with a space-frequency coding technique, one signalstream 510 may be generated for transmission from a first location, suchas the antenna 112 of FIG. 1, and a second signal stream 515 may begenerated for transmission from a second location, such as the antenna114 of FIG. 1. The relationship between the symbols in the streams 510and 515 is generally specified by the space-frequency coding technique.

Pilot symbols 520-525 are shown in the data stream 510, withcorresponding data symbols in the data stream 515. Data symbols 530-539are included in the data stream 510, with corresponding data symbols inthe data stream 515. The pilot symbols 520-525 have been insertedamongst the data symbols 530-539. Data symbols 530 and 531 have beenreplicated from one frequency to another frequency in the data streams510 and 515. The replicated data symbols have been inserted at alocation between the pilot symbols 523 and 524. As generally describedabove, any number or positioning of replicated data symbols maygenerally be used. In the example shown in FIG. 5, data symbols havebeen replicated in pairs. Replicating a pair of data symbols may beadvantageous in some examples for consistency with the coding techniqueemployed to code the data stream.

FIG. 6 is an example method for transmitting signals over acommunications channel arranged in accordance with an example of thepresent disclosure. The method may include one or more of blocks 605,610, 615, 620, and/or 625. The various blocks described herein may beperformed sequentially, in parallel, or in a different order than thosedescribed herein. It should also be appreciated that in someimplementations one or more of the illustrated blocks may be eliminated,combined or separated into additional blocks. The method 600 may includeblock 605, “Modulate data in accordance with an orthogonal frequencydivision multiplexing technique to generate multiple data streams.”Block 605 may be followed by block 610 “Insert pilot symbols into thedata streams.” Block 610 may be followed by block 615 “Replicate datafrom one data stream and insert the replicated data into another datastream.” Block 615 may be followed by block 620 “Encode the data streamsin accordance with a block encoding technique.” Block 620 may befollowed by block 625 “Transmit the data streams over a communicationschannel.”

Data may be modulated in accordance with an OFDM technique in block 605.The modulation may be performed, for example, by any suitable structurein a communications device, such as a DSP or other processing unit. Insome examples, one data stream may be generated for each antenna to beused in transmitting the data over the communications channel.

In block 610, pilot symbols may be inserted into the data streams. Theinsertion may be performed, for, example, by any suitable structure in acommunications device, including a mixer or multiplexor. Generally, thepilot symbols correspond to symbols known by the transmitting andreceiving devices of a communications system. By decoding signalsencoding a known pilot symbol, a receiving device may generate anestimate of the channel matrix of the communications channel. Pilotsymbols may be stored in any memory structure in communication with thecommunications device, or may be communicated to the communicationsdevice. Any number of pilot symbols may generally be inserted into thedata streams with substantially any spacing. The more pilot symbols areinserted into the data streams, the more the overall data transmissionrate of the communications system may decrease. However, in exampleshaving more pilot symbols inserted into the data streams, the estimatesof the channel matrix by a receiving communications device may be moreaccurate. Accordingly, there may be a tradeoff between data rate andaccuracy of the channel estimation. As will be described further below,use of replicated data symbols as pilot symbols may advantageouslyincrease the channel estimation accuracy while not impacting the overalldata rate as severely as using more pilot symbols.

In block 615, data may be replicated from one data stream and insertedinto another data stream. The replication may be performed by anysuitable structure in a communications device, including a mixer ormultiplexor for example. In some examples, a same structure may be usedto insert the replicated data as was used to insert the pilot symbols.The replicated data may include one or more symbols from a data stream.In some examples, pairs of symbols may be replicated. The data may beinserted such that it is transmitted at a same frequency band in each ofthe data streams. Any number of replicated data instances may beincluded in a transmission. As will be described further below, thereplicated data may be utilized to improve estimates of a channel matrixassociated with a communications channel. Accordingly, as morereplicated data is inserted, the accuracy of the channel matrix estimatemay increase. However, as more replicated data is inserted, the overalldata rate of the communications system may be reduced, although thereduction may not be as severe as if more known pilot symbols wereinserted. The replicated data may be inserted between two pilot symbols,and may be inserted at a midpoint between the two pilot symbols.However, the replicated data may be inserted at substantially anylocation in some examples.

In block 620, the data streams may be encoded in accordance with a blockencoding technique. The encoding may be performed by any suitablestructure in a communications device, for example by a DSP or otherprocessing unit. As described above, any block encoding technique may beused, including space-time coding or space-frequency coding.

In block 625, the data streams may be transmitted over a communicationschannel. The transmission may be performed by a transmitter acting incooperation with one or more antennas in some examples. In someexamples, each antenna may be used to transmit one of the data streams.

FIG. 7 is an example method for receiving signals over a communicationschannel arranged in accordance with an example of the presentdisclosure. The method 700 may include one or more of blocks 705, 710,715, 720, 725, and/or 730. The various blocks described herein may beperformed sequentially, in parallel, or in a different order than thosedescribed herein. It should also be appreciated that in someimplementations one or more of the illustrated blocks may be eliminated,combined or separated into additional blocks. The method 700 may includeblock 705 “Receiving a known pilot symbol over a communicationschannel.” Block 705 may be followed by block 710 “Estimating thecommunications channel based, at least in part, on the known pilotsymbol.” Block 710 may be followed by block 715 “Receiving replicateddata from multiple data streams over the communications channel.” Block715 may be followed by block 720 “Decoding the replicated data using theestimate of the communications channel.” Block 720 may be followed byblock 725 “Updating the estimate of the communications channel based, atleast in part, on the replicated data.” Block 725 may be followed byblock 730 “Decoding subsequently received data using the updated channelestimate.”

In block 705, a known pilot symbol may be received over a communicationschannel. The symbol may be received by any suitable receiver of acommunications device. Signals may generally be received that encode theknown pilot symbol. The received signals may also provide an indicationthat the encoded symbol is a pilot symbol.

In block 710, the communications channel may be estimated based, atleast in part, on the received pilot symbol. The estimation may beperformed by any suitable structure of a communications device, such asa DSP or other processing unit. Generally, all or a portion of a channelmatrix may be estimated by comparing a decoded received pilot symbolwith the known pilot symbol. Known pilot symbols may be stored at thecommunications device or otherwise communicated to the communicationsdevice for comparison with decoded pilot symbols received over thecommunications channel. The estimated channel, including data estimatingall or a portion of a channel matrix, may be stored in some examples.

In block 715, replicated data from multiple data streams may be receivedover the communications channel. Any suitable receiver may be used toreceive the replicated data. Examples of replicated data have beendescribed above. Generally, signals are received that may encode thereplicated data and the signals may also encode an indication that thedata includes one or more replicated data symbols. Signals encoding thereplicated data may be received by a single antenna in some examples.

In block 720, the replicated data may be decoded using the estimate ofthe communications channel. Any suitable structure of a communicationsdevice may be used to perform the decoding, such as a DSP or otherprocessing unit. In some examples, a joint detection technique is usedto decode the replicated data, such as max-ratio combining. By decodingmultiple copies of the replicated data, the decoding may be consideredto be more accurate than the decoding of single data symbols.Accordingly, the decoded replicated data may be used to generate orupdate an estimate of the communications channel.

In block 725, the estimate of the communications channel may be updatedbased, at least in part, on the replicated data. The updating may beperformed by any suitable structure in a communications device, such asa DSP or other processing unit. The estimate may be updated by comparingthe decoded symbol with the two instances of received signals encodingthe symbol. In this manner, the channel estimate may be generated orupdated, which may include all or a portion of the channel matrix. Theupdated channel estimate may be stored in some examples.

In block 730, subsequently received data may be decoded using theupdated channel estimate. That is, signals received following theupdating of the channel estimate may be decoded using the updatedchannel estimate. The updated channel estimate may improve decodingperformance in some examples.

Accordingly, examples have been described above of estimating acommunications channel based on pilot symbols and replicated datasymbols. In this manner, the number of pilot symbols may be effectivelyincreased through the use of replicated data symbols. The accuracy ofthe resultant channel estimates may in some examples approach theaccuracy of an example where the effective number of inserted pilotsymbols is equal to a sum of the number of pilot symbols plus the numberof inserted replicated data symbols. Because the replicated data symbolsalso transmit data over the communications channel, however, the use ofreplicated data symbols may not impair the overall data rate of thesystem as severely as the use of more pilot symbols.

FIG. 8 is a block diagram illustrating an example computing device 800that is arranged for generating an updated channel estimate inaccordance with examples of the present disclosure. In a very basicconfiguration 801, computing device 800 typically includes one or moreprocessors 810 and system memory 820. A memory bus 830 may be used forcommunicating between the processor 810 and the system memory 820.

Depending on the desired configuration, processor 810 may be of any typeincluding but not limited to a microprocessor (μP), a microcontroller(μC), a digital signal processor (DSP), or any combination thereof.Processor 810 may include one more levels of caching, such as a levelone cache 811 and a level two cache 812, a processor core 813, andregisters 814. An example processor core 813 may include an arithmeticlogic unit (ALU), a floating point unit (FPU), a digital signalprocessing core (DSP Core), or any combination thereof. An examplememory controller 815 may also be used with the processor 810, or insome implementations the memory controller 815 may be an internal partof the processor 810.

Depending on the desired configuration, the system memory 820 may be ofany type including but not limited to volatile memory (such as RAM),non-volatile memory (such as ROM, flash memory, etc.) or any combinationthereof. System memory 820 may include an operating system 821, one ormore applications 822, and program data 824. Application 822 may includea channel estimate routine 823 that is arranged to generate an estimateof a communications channel based on received pilot symbols, replicateddata symbols, or combinations thereof. Program Data 824 may includeknown pilot symbols 825, replicated data symbols 826, channel estimate827, or combinations thereof, that may be useful for generating channelestimates as generally described above. In some embodiments, application822 may be arranged to operate with program data 824 on an operatingsystem 821 such that channel estimates are generated and/or updated onthe basis of received pilot symbols and replicated data symbols. Thisdescribed basic configuration is illustrated in FIG. 8 by thosecomponents within dashed line 801.

Computing device 800 may have additional features or functionality, andadditional interfaces to facilitate communications between the basicconfiguration 801 and any required devices and interfaces. For example,a bus/interface controller 840 may be used to facilitate communicationsbetween the basic configuration 801 and one or more data storage devices850 via a storage interface bus 841. The data storage devices 850 may beremovable storage devices 851, non-removable storage devices 852, or acombination thereof. Examples of removable storage and non-removablestorage devices include magnetic disk devices such as flexible diskdrives and hard-disk drives (HDD), optical disk drives such as compactdisk (CD) drives or digital versatile disk (DVD) drives, solid statedrives (SSD), and tape drives to name a few. Example computer storagemedia may include volatile and nonvolatile, removable and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules, or other data.

System memory 820, removable storage 851 and non-removable storage 852are all examples of computer storage media. Computer storage mediaincludes, but is not limited to, RAM, ROM, EEPROM, flash memory or othermemory technology, CD-ROM, digital versatile disks (DVD) or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which maybe used to store the desired information and which may be accessed bycomputing device 800. Any such computer storage media may be part ofdevice 800.

Computing device 800 may also include an interface bus 842 forfacilitating communication from various interface devices (e.g., outputinterfaces, peripheral interfaces, and communication interfaces) to thebasic configuration 801 via the bus/interface controller 840. Exampleoutput devices 860 include a graphics processing unit 861 and an audioprocessing unit 862, which may be configured to communicate to variousexternal devices such as a display or speakers via one or more A/V ports863. Example peripheral interfaces 870 include a serial interfacecontroller 870 or a parallel interface controller 872, which may beconfigured to communicate with external devices such as input devices(e.g., keyboard, mouse, pen, voice input device, touch input device,etc.) or other peripheral devices (e.g., printer, scanner, etc.) via oneor more I/O ports 873. An example communication device 880 includes anetwork controller 881, which may be arranged to facilitatecommunications with one or more other computing devices 890 over anetwork communication link via one or more communication ports 882.

The network communication link may be one example of a communicationmedia. Communication media may typically be embodied by computerreadable instructions, data structures, program modules, or other datain a modulated data signal, such as a carrier wave or other transportmechanism, and may include any information delivery media. A “modulateddata signal” may be a signal that has one or more of its characteristicsset or changed in such a manner as to encode information in the signal.By way of example, and not limitation, communication media may includewired media such as a wired network or direct-wired connection, andwireless media such as acoustic, radio frequency (RF), microwave,infrared (IR) and other wireless media. The term computer readable mediaas used herein may include both storage media and communication media.

Computing device 800 may be implemented as a portion of a small-formfactor portable (or mobile) electronic device such as a cell phone, apersonal data assistant (PDA), a personal media player device, awireless web-watch device, a personal headset device, an applicationspecific device, or a hybrid device that include any of the abovefunctions. Computing device 800 may also be implemented as a personalcomputer including both laptop computer and non-laptop computerconfigurations.

The present disclosure is not to be limited in terms of the particularexamples described in this application, which are intended asillustrations of various aspects. Many modifications and examples canmay be made without departing from its spirit and scope, as will beapparent to those skilled in the art. Functionally equivalent methodsand apparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and examples are intended tofall within the scope of the appended claims. The present disclosure isto be limited only by the terms of the appended claims, along with thefull scope of equivalents to which such claims are entitled. It is to beunderstood that this disclosure is not limited to particular methods,reagents, compounds compositions or biological systems, which can, ofcourse, vary. It is also to be understood that the terminology usedherein is for the purpose of describing particular examples only, and isnot intended to be limiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.).

It will be further understood by those within the art that if a specificnumber of an introduced claim recitation is intended, such an intentwill be explicitly recited in the claim, and in the absence of suchrecitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to examples containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations).

Furthermore, in those instances where a convention analogous to “atleast one of A, B, and C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, and C”would include but not be limited to systems that have A alone, B alone,C alone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). In those instances where a conventionanalogous to “at least one of A, B, or C, etc.” is used, in general sucha construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, or C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the likeinclude the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember. Thus, for example, a group having 1-3 items refers to groupshaving 1, 2, or 3 items. Similarly, a group having 1-5 items refers togroups having 1, 2, 3, 4, or 5 items, and so forth.

While the foregoing detailed description has set forth various examplesof the devices and/or processes via the use of block diagrams,flowcharts, and/or examples, such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one example, severalportions of the subject matter described herein may be implemented viaApplication Specific Integrated Circuits (ASICs), Field ProgrammableGate Arrays (FPGAs), digital signal processors (DSPs), or otherintegrated formats. However, those skilled in the art will recognizethat some aspects of the examples disclosed herein, in whole or in part,can be equivalently implemented in integrated circuits, as one or morecomputer programs running on one or more computers (e.g., as one or moreprograms running on one or more computer systems), as one or moreprograms running on one or more processors (e.g., as one or moreprograms running on one or more microprocessors), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of skill in the art in light of this disclosure.For example, if a user determines that speed and accuracy are paramount,the user may opt for a mainly hardware and/or firmware vehicle; ifflexibility is paramount, the user may opt for a mainly softwareimplementation; or, yet again alternatively, the user may opt for somecombination of hardware, software, and/or firmware.

In addition, those skilled in the art will appreciate that themechanisms of the subject matter described herein are capable of beingdistributed as a program product in a variety of forms, and that anillustrative example of the subject matter described herein appliesregardless of the particular type of signal bearing medium used toactually carry out the distribution. Examples of a signal bearing mediuminclude, but are not limited to, the following: a recordable type mediumsuch as a floppy disk, a hard disk drive, a Compact Disc (CD), a DigitalVersatile Disk (DVD), a digital tape, a computer memory, etc.; and atransmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link, etc.).

Those skilled in the art will recognize that it is common within the artto describe devices and/or processes in the fashion set forth herein,and thereafter use engineering practices to integrate such describeddevices and/or processes into data processing systems. That is, at leasta portion of the devices and/or processes described herein can beintegrated into a data processing system via a reasonable amount ofexperimentation. Those having skill in the art will recognize that atypical data processing system generally includes one or more of asystem unit housing, a video display device, a memory such as volatileand non-volatile memory, processors such as microprocessors and digitalsignal processors, computational entities such as operating systems,drivers, graphical user interfaces, and applications programs, one ormore interaction devices, such as a touch pad or screen, and/or controlsystems including feedback loops and control motors (e.g., feedback forsensing position and/or velocity; control motors for moving and/oradjusting components and/or quantities). A typical data processingsystem may be implemented utilizing any suitable commercially availablecomponents, such as those typically found in datacomputing/communication and/or network computing/communication systems.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely examples, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

While various aspects and examples have been disclosed herein, otheraspects and examples will be apparent to those skilled in the art. Thevarious aspects and examples disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A method of transmitting data over a communications channel, the method comprising: modulating data for transmission over the communications channel in accordance with an orthogonal frequency division multiplexing technique to generate at least a first and second data stream for transmission using respective transmit antennas; inserting at least a portion of data from the first data stream into the second data stream; and transmitting the first and second data streams over the communications channel.
 2. The method of claim 1, further comprising: inserting pilot symbols into the first and second data streams.
 3. The method of claim 2 wherein said inserting at least a portion of data from the first data stream into the second data stream comprises inserting the portion of data from the first data stream into the second data stream at a location between two pilot symbols in the second data stream.
 4. The method of claim 3 wherein said inserting at least a portion of data from the first data stream into the second data stream comprises inserting a respective portion of data from the first data stream into the second data stream between each two pilot symbols in the second data stream.
 5. The method of claim 1 further comprising encoding the first and the second data streams in accordance with a block coding technique.
 6. The method of claim 5 wherein the block coding technique comprises a space-time block coding technique.
 7. The method of claim 5 wherein the block coding technique comprises a space-frequency block coding technique.
 8. A method of decoding a signal transmitted over a communications channel, the method comprising: receiving a pilot symbol over the communications channel; estimating a channel matrix of the communications channel based, at least in part, on the pilot symbol; receiving replicated data from multiple data streams transmitted over the communications channel; decoding the replicated data using the estimated channel matrix; and generating an updated estimate of the channel matrix based, at least in part, on the replicated data.
 9. The method of claim 8, further comprising decoding subsequently received signals over the communications channel using the updated estimate of the channel matrix.
 10. The method of claim 8 wherein said decoding the replicated data comprises using a joint detection technique.
 11. The method of claim 8, wherein said decoding the replicated data comprises using a space-time block decoding technique.
 12. The method of claim 8, wherein said decoding the replicated data comprises using a space-frequency block decoding technique.
 13. The method of claim 8, wherein the replicated data includes same data symbols in multiple data streams.
 14. A communication device comprising: a modulator configured to modulate data in accordance with an orthogonal frequency division multiplexing technique for transmission over a communications channel using at least a first and a second transmit antenna, wherein the modulator is further configured to generate at least a first data stream for transmission with the first antenna and a second data stream for transmission with the second antenna; a replicator coupled to the modulator and configured to receive the first and second data streams, wherein the replicator is configured to insert at least one data symbol from the first data stream into the second data stream; an encoder coupled to the replicator and configured to receive the first and second data streams including the inserted at least one symbol, wherein the encoder is configured to encode the first and second data streams in accordance with a block coding technique; and a transmitter coupled to the encoder and configured to receive the encoded first and second data streams, wherein the transmitter is configured to transmit the first data stream over the communications channel using the first antenna and further configured to transmit the second data stream including the inserted at least one symbol over the communications channel using the second antenna.
 15. The communication device of claim 14 wherein the block coding technique comprises a space-time encoding technique.
 16. The communication device of claim 14 wherein the block coding technique comprises a space-frequency encoding technique.
 17. The communication device of claim 14 wherein the first and second data streams further include at least two pilot symbols, and wherein the replicator is configured to insert the at least one data symbol between the at least two pilot symbols.
 18. A communication device comprising: a receiver configured to receive signals over a communications channel, wherein the signals are based at least in part on first and second data streams transmitted over a communications channel, wherein the second data stream includes at least one data symbol replicated from the first data stream; a decoder coupled to the receiver and the channel estimator, wherein the decoder is configured to receive the received signals and decode the at least one data symbol replicated from the first data stream; a channel estimator coupled to the decoder and the receiver, wherein the channel estimator is configured to receive the received signals and the decoded at least one data symbol, wherein the channel estimator is configured to estimate a channel matrix of the communications channel based, at least in part, on the decoded at least one data symbol; and wherein the decoder is further configured to decode subsequent received signals based, at least in part, on the estimate of the channel matrix.
 19. The communication device of claim 18 wherein the decoder is configured to decode the at least one data symbol using a joint detection technique.
 20. The communication device of claim 18 wherein the first and second data streams each further include at least one pilot symbol, and wherein the channel estimator is configured to receive the at least one pilot symbol and generate an initial estimate of the channel matrix based, at least in part on the at least one pilot symbol. 